Vivus Inc. (VVUS), maker of the obesity drug Qsymia, said it’s in talks with large pharmaceutical companies to explore ways to increase use of the medicine amid investor unrest over disappointing sales. The shares rose the most in five months. Approved in July, Qsymia was the second obesity therapy to clear the U.S. Food and Drug Administration since 1999. Sales have lagged behind analysts’ estimates, coming in at $4.1 million in the first quarter, the Mountain View, California-based company said today. Six analysts had estimated $4.5 million, the average of projections compiled by Bloomberg. “We’ve begun discussions with large pharmaceutical companies to explore how we can increase efforts with primary care physicians, which we believe is critical to maximizing the value of Qsymia,” Vivus Chief Executive Officer Leland Wilson said today on a conference call.